Technical Field
[0001] The present invention is in the field of machine dishwashing. More specifically,
the invention encompasses automatic dishwashing tablets.
Background of the Invention
[0002] A re-current problem with tablets is to obtain a tablet that dissolves quickly when
added to the main wash of the machine but with sufficient strength so it does not
crumble on storage or handling.
[0003] Attempts to optimize the performance of tablet technology have primarily been directed
towards modification of the dissolution profile of tablets. This is deemed especially
important for those tablets that are placed in the dispenser of the machine so that
they come into contact with a water spray at the very beginning of the wash process.
EP-A-264, 701 describe machine dishwashing tablets comprising anhydrous and hydrated
metasilicates, anhydrous triphosphate, active chlorine compounds and a tabletting
aid consisting of a mixture of sodium acetate and spray-dried sodium zeolite. The
specification teaches in warm water at least 65% of the tablet is available for the
cleaning stage of the wash.
[0004] DE-A-4229650 describes a tablet comprising tripolyphosphate hexahydrate and water-free
silicate and optional cleaning components and tabletting auxiliaries. The tablets
are said to exhibit rapid dissolution.
[0005] The technology of the present invention provides fast dissolving tablets that clean
well and do not crumble.
Description of the Invention
[0006] Accordingly, the present invention provides a process for preparing a tablet comprising:
the step of compacting a composition comprising:
a) particles containing sodium tripolyphosphate having a water of hydration in an
amount from 1% to 5% by weight and wherein at least 50% by weight of the sodium tripolyphosphate
within the particles is of a phase I form;
b) 0.1 to 2 wt.% of the total composition of a ketone which has at least 25 carbon
atoms and;
c) 0.5 to 10 wt. % of the total composition of an anionic surfactant, in which the
anionic surfactant is in powdered form and has a particle size such that the length
of the particle is at least 1400 microns and the width of the particle is less or
equal to 250 microns.
[0007] In the most preferred aspect of this invention the tablet is for use in a machine
dishwasher.
Detailed Description of the Invention
I. Sodium Tripolyphosphate with High Phase I Content
[0008] Sodium tripolyphosphate can be converted to the phase I form by heating to above
the transition temperature at which phase II anhydrous sodium polyphosphate is transformed
into the phase I form. A process for the manufacture of particles containing a high
proportion of the phase I form of sodium tripolyphosphate by spray drying below 420°C
is given in US-A-4536377.
[0009] Suitable material is commercially available. Suppliers include Rhodia, Courbevoie,
France and Albright & Wilson, Warley, West Midlands, UK. The sodium tripolyphosphate
should be partially hydrated, but the phase I anhydrous form should also be present.
Thus, the sodium tripolyphosphate in the particles may incorporate up to 5% (by weight
of the sodium tripolyphosphate in these particles) of water of hydration. The extent
of hydration is from 1% to 5% by weight. This degree of hydration in general means
that the sodium tripolyphosphate is partially hydrated.
[0010] The sodium tripolyphosphate in these particles is preferably hydrated by a process,
which leads to a homogeneous distribution of the water of hydration within the tripolyphosphate.
[0011] This can be accomplished by exposing anhydrous sodium tripolyphosphate to steam or
moist air. The particles preferably consist solely of sodium tripolyphosphate with
a high content of the phase I form. The phase I content of the sodium tripolyphosphate
being measured by X-ray diffraction, or IR.
[0012] The particles preferably contain sodium tripolyphosphate in a porous form so as to
have high surface area. This can be achieved by spray drying the tripolyphosphate
as a mixture with a blowing agent, that is a compound such as ammonium carbonate,
which decomposes to yield a gas during the course of the spray drying. This gives
the dried material a porous structure, with higher surface area than hollow beads
of tripolyphosphate obtained without blowing agent.
[0013] The bulk density of the of sodium tripolyphosphate particles is preferably 0.75 Kg/M
3 or less, more preferably from 0.52 to 0.72 Kg/M
3.
[0014] The particles which contain or consist of sodium tripolyphosphate preferably have
a small mean particle size, such as not over 300µm, better not over 250µm. Small particle
size can if necessary be achieved by grinding.
[0015] Uniform prehydration, high phase I content porosity and small particle size all promote
rapid hydration when the tripolyphosphate comes into contact with water. A standard
test for the rapidity of hydration is the Olten test. It is desirable that in such
a test the tripolyphosphate reaches 90% of the final value (i.e. 90% of complete hydration
when exposed to water at 80°C) within 60 seconds.
[0016] "Rhodiaphos HPA 3.5" is a grade of sodium tripolyphosphate from Rhodia which has
been found to be particularly suitable. It consists of porous particles of small particle
size (mean size below 250µm) with 70% phase I and prehydrated with 3.5% water of hydration.
[0017] Preferably the said particles containing sodium tripolyphosphate with more than 50%
of phase I material provide this phase I tripolyphosphate as at least 3% by weight
of the tablet or region thereof. More preferably they provide sodium tripolyphosphate,
including the phase I tripolyphosphate, in a quantity which is from 30% up to 40%
or 60% by weight of the tablet or region thereof.
[0018] The remainder of the tablet composition may include additional sodium tripolyphosphate.
This may be in any form, including anhydrous sodium tripolyphosphate with a high content
of the phase II form, hydrated sodium tripolyphosphate or some combination of the
two.
[0019] The total quantity of sodium tripolyphosphate, in all forms, present in the composition
of a tablet or a region thereof will generally lie in a range from 15% to 85% by weight,
more preferably at al level of 30 to 75 wt%. It is especially preferable if the total
level of phosphate is greater than 60-wt% of the tablet.
Surfactant material
[0020] An anionic surfactant is present as an essential feature of the tablet.
[0021] Suitable anionic surfactants are listed in standard texts such as Surfactants in
Consumer Products; Theory, Technology and Application, J. Falbe, ed. Springer-Verlag
1987 and Handbook of Surfactants, M.R. Porter, Blackie & Son, 1991.
[0022] Preferred anionic surfactants include the conventional C11-C18 alkyl benzene sulfonates
and primary, secondary and random alkyl sulfates, the C
8-C
18 alkyl alkoxy sulfates and the C
8-C
18 alpha-sulfonated fatty acid esters and the like.
[0023] Especially preferred is the sodium salt of a C
10 -C
22 sulphate, such as sodium lauryl sulphate (SLS).
[0024] The anionic surfactant is in powdered form and has a particle size such that the
length of the particles is at least 1400 microns and the width is a maximum of 250
microns.
[0025] It is also advantageous if the anionic surfactant has a density at 25°C from 0.25
to 0.6 g/cm, preferably 0.4 to 0.6 g/cm.
[0026] The anionic surfactant is present at levels from 0.5 to 10 wt% of the total composition,
more preferably from 0.5 to 3 wt%.
[0027] Other surfactant systems comprising surfactants selected from nonionic, cationic,
ampholytic and zwitterionic surfactants and mixtures thereof may also be present in
the composition at levels of 5 wt% of the total composition or less.
[0028] Suitable low to non-foaming nonionic surfactants, include any alkoxylated nonionic
surface-active agent wherein the alkoxy moiety is selected from the group consisting
of ethylene oxide, propylene oxide and mixtures thereof. This nonionic surfactant
is used to improve the detergency. Preferably the level of nonionic surfactant is
at least 0.1% by weight, more preferably at least 0.5% by weight.
[0029] Examples of suitable nonionic surfactants for use in the invention are the low- to
non-foaming ethoxylated straight-chain alcohols preferred nonionic surfactants are
Plurafac LF series ex BASF, the Synperonic series ex ICI; Lutensol® LF series, ex
BASF Company and the Triton® DF series, ex Rohm & Haas Company.
The Ketone.
[0030] The ketones of the tablet are obtained by the ketonization of C
16-C
22 carboxylic acids, carboxylic acid salts and mixtures thereof.
[0031] The long-chain ketones may be prepared as described in US-A- 4,937,011. The ketones
are prepared by catalytic elimination of CO
2 from higher monocarboxylic acids, more particularly relatively high molecular weight
fatty acids or salts thereof.
[0032] Preferred ketones are those obtained by the reaction of linear or branched, saturated
or unsaturated carboxylic acids or carboxylic acid mixtures in which the carboxylic
acids or some of them contain more than 12 carbon atoms and in particular, have a
carbon chain-length of C
14 to C
30 and, on ketonization, react with water with elimination of carbon dioxide. Particularly
preferred ketones are those obtained by the ketonization of C
16-C
22 carboxylic acids or carboxylic acid salts and mixtures thereof as described in US-A-4,937,011.
[0033] Mixtures of symmetrical and asymmetrical ketones are formed in which the asymmetrical
ketones, commensurate with the material used, may have chain lengths other than C
14 or C
12 provided that a relatively long-chain radical is present in the molecule so that
the total number of carbon atoms on average is at least about 25. Examples are heptacosanone-14,
hentriacontanone-16, pentatriacontanone-18, nonatriacontanone-20, triatetracontanone-22
or nonacossanone-15, tri-triacontanone-17, heptatriacontanone-19, hentetracontanone-21
and the like.
[0034] Ketones or ketone mixtures useful in the tablet are normally solid at room temperature
and have melting points in the range from 60° to 105°C. To make them easier to process
and to improve their foam-inhibiting effect, it is preferred to disperse the ketones
in a liquid carrier. In addition to water, suitable liquid phases are preferably organic
carriers which have a low pour point or melting point of lower than about 5°C. It
is also preferable to use free-flowing carriers or carrier mixtures which have a comparatively
high viscosity and contribute stabilization of the dispersions. The liquid carrier
phase may also have a foam-inhibiting effect or may be used solely as a carrier for
the foam inhibitor.
[0035] Particularly useful organic carrier liquids, which have an additional foam-inhibiting
effect, are mineral oils having a boiling point above 140°C and branched alcohols
containing 8 to 24 carbon atoms, such as 2-hexyl-1-decanol or 2-octyl-2-dodecanol.
Other useful foam-inhibiting carrier liquids are liquid esters of branched or unsaturated
fatty acids containing 8 to 18 carbon atoms with monohydric or polyhydric alcohols,
for example glycol diesters or glycerol triesters of oleic acid, isostearic acid;
esters based on branched-chain or unsaturated, liquid fatty alcohols containing 8
to 18 carbon atoms, for example isotridecyl alcohol or oleyl alcohol. Mixtures of
these carriers may also be used.
[0036] It is preferred to use organic carriers in which the ketones are soluble at elevated
temperature and precipitate in finely divided form on cooling. To this end, the components
are heated, a solution formed and then rapidly cooled with intensive stirring. Stable
dispersions of finely divided foam inhibitors are formed. However, dispersions may
also be prepared by stirring the finely ground, wax-like ketone or ketone mixture
into the liquid phase.
[0037] The dispersions to be processed preferably contain from about 5 to about 15% by weight
of the ketone or mixtures of ketones. The carrier/ketone combination is present in
the detergent composition in an amount of from 0.1 to 2 wt.%.
[0038] In addition, the dispersion of the ketone in the liquid carrier may be stabilized
by suitable additives. Suitable additives are, for example, magnesium stearate, calcium
stearate or aluminum stearate in quantities of from about 0.3 to 3.0% by weight.
[0039] Commercially available ketones of the type described above are available under the
Dehypon® Series from Henkel Kommanditgesellschaft auf Aktien, Germany.
Builder material
[0040] In addition to sodium tripolyphosphate further builders may be present.
[0041] Suitable additional builders are the carboxylate or polycarboxylate builders containing
from one to four carboxy groups, particularly selected from monomeric polycarboxylates
or their acid forms, homo or copolymeric polycarboxylic acids or there salts in which
the polycarboxylate comprises at least two carboxylic radicals selected from each
other by not more than two carbon atoms. Preferred carboxylates include the polycarboxylate
materials described in US-A-2,264,103, including the water-soluble alkali metal salts
of mellitic acid and citric acid, dipicolinic acid, oxydisuccinic acid and alkenyl
succinates. The water-soluble salts of polycarboxylate polymers and copolymers, such
as are described in US-A-3,308,067 are also be suitable for use with the invention.
Of the builder materials listed in the above paragraph, the preferred polycarboxylates
are hydroxycarboxylates containing up to three carboxy groups per molecule, especially
citric acid or its salt, particularly sodium citrate. If present it is preferable
if the carboxylate builder is present at a level of at least 20-wt% of the total formulation,
more preferably at a level greater than 30-wt%.
[0042] Further soluble detergency builder salts which can be used are poly-valent inorganic
and poly-valent organic builders, or mixtures thereof. Non-limiting examples of suitable
water-soluble, inorganic alkaline detergency builder salts include the alkali metal
carbonates, bicarbonates, borates, phosphates, polyphosphates, tripolyphosphates,
and phosphono carboxylates. Specific examples of such salts include the sodium and
potassium tetraborates, carbonates, bicarbonates tripolyphosphates, orthophosphates
and hexametaphosphates. Other suitable detergency builders organic alkaline compounds
such as water-soluble amino polyacetates, e.g. sodium and potassium ethylenediamine
tetraacetates, nitrilotriacetates and N- (2-hydroxyethyl)nitrilodiacetates; water-soluble
salts of phytic acid, e.g. sodium and potassium phytates; water-soluble polyphosphonates,
including sodium, potassium and lithium salts of ethane-1-hydroxy-1,1-diphosphonic
acid; sodium, potassium and lithium salts of methylenediphosphonic acid and the like.
[0043] It is to be understood that, while the alkali metal salts of the foregoing inorganic
and organic poly-valent anionic builder salts are preferred for use herein from an
economic standpoint, the ammonium, alkanolammonium, e.g. triethanolammonium, diethanolammonium,
and the like, water-soluble salts of any of the foregoing builder anions are useful
herein.
[0044] Mixtures of organic and/or inorganic builder salts can be used herein.
[0045] Preferably, the total amount of builders in the composition including the particles
containing sodium tripolyphosphate (having a water of hydration in an amount from
1% to 5% by weight and wherein at least 50% by weight of the sodium tripolyphosphate
within the particles is of a phase I form) is from 30 to 80% by weight, more preferably
from 40 to about 70% by weight.
Silica material
[0046] Suitable forms of silica include amorphous silica, such as precipitated silica, pyrogenic
silica and silica gels, such as hydrogels, xerogels and aerogels, or the pure crystal
forms quartz, tridymite or crystobalite, but the amorphous forms of silica are preferred.
Suitable silicas may readily be obtained commercially. They are sold, for example
under the Registered Trade Name Gasil 200 (ex Crosfield, UK).
[0047] Preferably, the silica is in the product in such a form that it can dissolve when
added to the wash liquor. Therefore, addition of silica by way of addition anti-foam
particles of silica and silicone oil is not preferred.
[0048] The particle size of the silica material may be of importance, especially as it is
believed that any silica material that remains undissolved during the washing process,
may deposit on the glass at a later stage. Therefore, it is preferred that silica
material are used that have a particle size (as determined with a Malvern Laser, i.e.
"aggregated" particles size) of at most 40 µm, more preferably at most 30µm, most
preferably at most 20µm provides better results in the wash. In view of incorporation
in a cleaning composition, it is preferred that the particle size of the silica material
is at least 1µm, more preferably at least 2µm, most preferably at least 5µm.
[0049] Preferably the primarily particle size of the silica is in general less than about
30nm, in particular less than about 25nm. Preferably, elementary particles size are
less than 20nm or even 10nm. There is no critical lower limit of the elementary particle
size; the lower limit is governed by other factors such as the manner of manufacture,
etc. In general commercial available silicas have elementary particle sizes of 1 nm
or more. ,
[0050] Preferably, the silica material is present in the wash liquor at a level of at least
2.5x10
-4%, more preferably at least 12.5x10
-4%, most preferably at least 2.5x10
-3% by weight of the wash liquor and preferably at most 1x10
-1%, more preferably at most 8x10
-2%, most preferably at most 5x10
-2% by weight of the wash liquor.
[0051] Preferably, the level of dissolved silica material in the wash liquor is at least
80 ppm, more preferably at least 100 ppm, most preferably at least 120 ppm and preferably
at most 1,000 ppm. It is noted that for the silica material to be effective, the lower
level of dissolved silica material depends on the pH value, i.e. thus at pH 6.5, the
level is preferably at least 100 ppm; at pH 7.0 preferably at least 110 ppm; at pH
7.5 preferably at least 120 ppm; at pH 9.5 preferably at least 200 ppm; at pH 10 preferably
at least 300 ppm; at pH 10.5 preferably at least 400ppm.
[0052] Preferably, the silica material is present in the cleaning composition at a level
of at least 0.1%, more preferably at least 0.5%, most preferably at least 1% by weight
of the cleaning composition and preferably at most 10%, more preferably at most 8%,
most preferably at most 5% by weight of the cleaning composition.
Silicates
[0053] The composition optionally comprises alkali metal silicates. The alkali metal may
provide pH adjusting capability and protection against corrosion of metals and against
attack on dishware, including fine china and glassware benefits. If silicates are
present, they are preferably included at a level of from 1% to 30%, preferably from
2% to 20%, more preferably from 3% to 10%, based on the weight of the composition.
The ratio of SiO
2 to the alkali metal oxide (M
2O, where M=alkali metal) is typically from 1 to 3.5, preferably from 1.6 to 3, more
preferably from 2 to 2.8. Preferably, the alkali metal silicate is hydrous, having
from 15% to 25% water, more preferably, from 17% to 20%.
[0054] The highly alkali metasilicates can in general be employed, although the less alkaline
hydrous alkali metal silicates having a SiO
2:M
2O ratio of from 2.0 to 2.4 are, as noted, greatly preferred. Anhydrous forms of the
alkali metal silicates with a SiO
2:M
2O ratio of 2.0 or more are also less preferred because they tend to be significantly
less soluble than the hydrous alkali metal silicates having the same ratio.
[0055] Sodium and potassium, and especially sodium, silicates are preferred. A particularly
preferred alkali metal silicate is a granular hydrous sodium silicate having a SiO
2:Na
2O ratio of from 2.0 to 2.4 available from Ak30 PQ Corporation, especially preferred
is Britesil H20 and Britesil H24. Most preferred is a granular hydrous sodium silicate
having a SiO
2:Na
2O ratio of 2.0. While typical forms, i.e. powder and granular, of hydrous silicate
particles are suitable, preferred silicate particles having a mean particle size between
300 and 900 microns and less than 40% smaller than 150 microns and less than 5% larger
than 1700 microns. Particularly preferred is a silicate particle with a mean particle
size between 400 and 700 microns with less than 20% smaller than 150 microns and less
than 1% larger then 1700 microns. Compositions having a pH of 9 or less preferably
will be substantially free of alkali metal silicate.
Enzymes
[0056] Enzymes may be present in the compositions. Examples of enzymes suitable for use
in the cleaning compositions include lipases, peptidases, amylases (amylolytic enzymes)
and others which degrade, alter or facilitate the degradation or alteration of biochemical
soils and stains encountered in cleansing situations so as to remove more easily the
soil or stain from the object being washed and to make the soil or stain more removable
in a subsequent cleansing step.
[0057] Preferred Examples of these enzymes are lipases, amylases and proteases. The enzymes
most commonly used in machine dishwashing compositions are amylolytic enzymes. Preferably,
the composition also contains a proteolytic enzyme. Enzymes may be present in a weight
percentage amount of from 0.2 to 5% by weight. For amylolytic enzymes, the final composition
will have amylolytic activity of from 10
2 to 10
6 Maltose units/kg. For proteolytic enzymes the final composition will have proteolytic
enzyme activity of from 10
6 to 10
9 Glycine Units/kg.
Bleach Material
[0058] Bleach material may optionally and preferably be incorporated in composition for
use in processes according to the present invention. These materials may be incorporated
in solid form or in the form of encapsulates and less preferably in dissolved form.
[0059] The bleach material may be a chlorine- or bromine-releasing agent or a peroxygen
compound. Peroxygen based bleach materials are however preferred.
[0060] Organic peroxy acids or the precursors therefor are typically utilized as the bleach
material. The peroxyacids usable in the present invention are solid and, preferably,
substantially water-insoluble compounds. By "substantially water-insoluble" is meant
herein a water-solubility of less than about 1% by weight at ambient temperature.
In general, peroxyacids containing at least about 7 carbon atoms are sufficiently
insoluble in water for use herein.
[0061] Inorganic peroxygen-generating compounds are also typically used as the bleaching
material. Examples of these materials are salts of monopersulphate, perborate monohydrate,
perborate tetrahydrate, and percarbonate.
[0062] Monoperoxy acids useful herein include alkyl peroxy acids and aryl peroxyacids such
as peroxybenzoic acid and ring-substituted peroxybenzoic acids (e.g. peroxy-alpha-naphthoic
acid); aliphatic and substituted aliphatic monoperoxy acids (e.g. peroxylauric acid
and peroxystearic acid); and phthaloyl amido peroxy caproic acid (PAP). Typical diperoxy
acids useful herein include alkyl diperoxy acids and aryldiperoxy acids, such as 1,12-di-peroxy-dodecanedioic
acid (DPDA); 1,9-diperoxyazelaic acid, diperoxybrassylic acid, diperoxysebacic acid
and diperoxy-isophthalic acid; and 2-decyldiperoxybutane-1,4-dioic acid.
[0063] Peroxyacid bleach precursors are well known in the art. As non-limiting examples
can be named N,N,N',N'-tetraacetyl ethylene diamine (TAED), sodium nonanoyloxybenzene
sulphonate (SNOBS), sodium benzoyloxybenzene sulphonate (SBOBS) and the cationic peroxyacid
precursor (SPCC) as described in US-A-4,751,015.
[0064] If desirably a bleach catalyst, such as the manganese complex, e.g. Mn-Me TACN, as
described in EP-A-0458397, or the sulphonimines of US-A-5,041,232 and US-A-5,047,163,
is to be incorporated, this may be presented in the form of a second encapsulate separately
from the bleach capsule or granule. Cobalt catalysts can also be used.
[0065] Among suitable reactive chlorine- or bromine-oxidizing materials are heterocyclic
N-bromo and N-chloro imides such as trichloroisocyanuric, tribromoisocyanuric, dibromoisocyanuric
and dichloroisocyanuric acids, and salts thereof with water-solubilizing cations such
as potassium and sodium. Hydantoin compounds such as 1,3-dichloro-5,5-dimethyl-hydantoin
are also quite suitable.
[0066] Particulate, water-soluble anhydrous inorganic salts are likewise suitable for use
herein such as lithium, sodium or calcium hypochlorite and hypobromite. Chlorinated
trisodium phosphate and chloroisocyanurates are also suitable bleaching materials.
[0067] Encapsulation techniques are known for both peroxygen and chlorine bleaches, e.g.
as described in US-A-4,126,573, US-A-4,327,151, US-A-3,983,254, US-A-4,279,764, US-A-3,036,013
and EP-A-0,436,971 and EP-A-0,510,761. However, encapsulation techniques are particularly
useful when using halogen based bleaching systems.
[0068] Chlorine bleaches, the compositions may comprise from about 0.5% to about 3% avCl
(available Chlorine). For peroxygen bleaching agents a suitable range are also from
0.5% to 3% AvO (available Oxygen). Preferably, the amount of bleach material in the
wash liquor is at least 12.5x10
-4% and at most 0.03% AvO by weight of the liquor.
Water Soluble Polymeric Polycarboxylic Compounds
[0069] A water soluble polymeric polycarboxylic compound is advantageously present in the
dish wash composition. Preferably these compounds are homo- or co-polymers of polycarboxylic
compounds, especially co-polymeric compounds in which the acid monomer comprises two
or more carboxyl groups separated by not more than two carbon atoms. Salts of these
materials can also be used.
[0070] Particularly preferred polymeric polycarboxylates are co-polymers derived from monomers
of acrylic acid and maleic acid. the average molecular weight of these polymers in
the acid form preferably ranges from 4,000 to 70,000.
[0071] Another type of polymeric polycarboxylic compounds suitable for use in the composition
are homopolymeric polycarboxylic acid compounds with acrylic acid as the monomeric
unit. The average weight of such homopolymers in the acid form preferably ranges from
1,000 to 100,000 particularly from 3,000 to 10,000.
[0072] Acrylic sulphonated polymers as described in EP 851 022 (Unilever) are also suitable.
[0073] Preferably, this polymeric material is present at a level of at least 0.1%, more
preferably at levels from 1 wt% to 7 wt% of the total composition.
Chelating Agent
[0074] A chelating agent may be present in the composition. If present it is preferable
if the level of chelating agent is from 0.5 to 3 wt% of the total composition.
[0075] Preferred chelating agents include organic phosphonates, amino carboxylates, polyfunctionally-substituted
compounds, and mixtures thereof.
[0076] Particularly preferred chelating agents are organic phosphonates such as α-hydroxy-2
phenyl ethyl diphosphonate, ethylene diphosphonate, hydroxy 1,1-hexylidene, vinylidene
1,1 diphosphonate, 1,2 dihydroxyethane 1,1 diphosphonate and hydroxy-ethylene 1,1
diphosphonate. Most preferred are hydroxy-ethylene 1,1 diphosphonate and 2 phosphono-1,2,4
butanetricarboxylic acid or salts there of.
Anti-tarnishing Agents
[0077] Anti-tarnishing agents such as benzotriazole and those described in EP 723 577 (Unilever)
may also be included.
Optional Ingredients
[0078] Optional ingredients are, for example, buffering agents, reducing agents, e.g., borates,
alkali metal hydroxide and the well-known enzyme stabilisers such as the polyalcohols,
e.g. glycerol and borax; anti-scaling agents; crystal-growth inhibitors, threshold
agents; thickening agents; perfumes and dyestuffs and the like.
[0079] Reducing agents may e.g. be used to prevent the appearance of an enzyme-deactivating
concentration of oxidant bleach compound. Suitable agents include reducing sulphur-oxy
acids and salts thereof. Most preferred for reasons of availability, low cost, and
high performance are the alkali metal and ammonium salts of sulphuroxy acids including
ammonium sulphite ((NH
4)
2SO
3), sodium sulphite (Na
2SO
3), sodium bisulphite (NaHSO
3), sodium metabisulphite (Na
2S
2O
3), potassium metabisulphite (K
2S
2O
5), lithium hydrosulphite (Li
2S
2O
4), etc., sodium sulphite being particularly preferred. Another useful reducing agent,
though not particularly preferred for reasons of cost, is ascorbic acid. The amount
of reducing agents to be used may vary from case to case depending on the type of
bleach and the form it is in, but normally a range of about 0.01% to about 1.0% by
weight, preferably from about 0.02% to about 0.5% by weight, will be sufficient.
pH of wash liquor
[0080] The invention relates to washing processes in mechanical dish washing machines in
which the pH of the wash liquor is preferably higher than about 8, more preferably
9 or higher, most preferably 10 or higher. Preferably the pH is lower than about 12.
The most advantageous pH range is from 9.5 to 11.
Temperature of washing process
[0081] The present invention preferably relates to processes of mechanically washing soiled
articles with a wash liquor at a temperature of at least 40°C, more preferably at
least 50°C, most preferably at least 55°C.
[0082] The invention will now be illustrated by the following non limiting Examples. Examples
of the invention are illustrated by a number, comparative Examples are illustrated
by a letter.
[0083] The following compositions were compressed to give tablets:
[0084] The mass of all the tablets was 25g.
- SLS is sodium lauryl sulphate
- Sokalan PA 25 CL is a polyacrylate.
- Dehypon 2429 is a long chain ketone in a fatty alcohol carrier.
[0085] The strength of the tablet was on a MTS Synergie 100. This machine uses a loadcell
of 500 N maximum capacity. The initial -and secondary crosshead speeds are set at
25 mm/min, with a deformation limit of 200%. Break-sensitivity is 10%. The tablet
is broken standing upright with its small side surfaces between the upper and lower
plates
[0086] The dissolution time was measured in a Bauknecht GSF 1161 (at 55°C) machine, loaded
with on-glaze decorated porcelain, glass, plates plus cutlery stainless steel articles
and plastics. The tablet to be tested was placed on the floor of the machine and the
weight of the tablet recorded as a function of time.
[0087] When the SLS is in the form of needles, that is if the length of the particles is
at least 1400 microns and the width is a maximum of 250 microns, the disintegration
time of the tablet is decreased as shown in the table below.
[0088] Table 2 shows the time taken for 100 % of the tablet to disintegrate. (Both tablets
pressed using 6 tons).
Table 2
|
Time (Mins) |
Tablet A |
18 |
Tablet 1 |
8 |
[0089] The tablet strength is increased if a solvent such as polybutylene diol is included.
Table 3
|
Strength (Newtons) |
Tablet A |
325 |
Tablet 2 |
350 |
[0090] Press force used to manufacture the tablets is 6 Tonnes.